Re: What trigge fsync of file on last close of the open inode?

[Jeremy Allison <jra@samba.org>]

On Tue, Oct 03, 2006 at 03:45:49PM -0500, Steve French wrote:
> Dave Kleikamp wrote:
> >>Someone had reported a problem with a writepages call coming in on with 
> >>no open files (so presumably the file was closed, with dirty pages not 
> >>written).
> >>    
> >
> >This is normal behavior for most file systems.  I thought cifs protected
> >this by flushing dirty data in cifs_close.  I don't think any data
> >should be dirtied after cifs_close is called (on the last open file
> >handle).
> >  
> I found it ...
> 
> cifs exports flush, filp_close calls flush (before calling close)
> 
> cifs_flush calls filemap_fdatawrite
> 
> May be a case in which filemap_fdatawrite returns before the write(s) is 
> sent to the vfs and write races with close (although cifs will defer a 
> file close if a write is pending on that handle)?

Steve,

	Here's a comment I found in the NFSv4 code.... might be relevent.

>From /usr/src/linux/fs/nfs/nfs4proc.c

/*
 * It is possible for data to be read/written from a mem-mapped file
 * after the sys_close call (which hits the vfs layer as a flush).
 * This means that we can't safely call nfsv4 close on a file until
 * the inode is cleared.